1. Field of the Invention
The present invention relates to a storage apparatus and its data verification method. The invention is suited for application in a storage apparatus for verifying data recorded on hard disk drives.
2. Description of Related Art
In recent years, as the information society has progressed, the amount of data from a host computer to be stored in storage apparatuses has been rapidly increasing. As a result of this situation, expansion in scale of the storage capacity of storage apparatuses is being promoted. An attempt has been made to expand the scale of the storage capacity of storage apparatuses by operating the storage apparatuses according to the RAID (Redundant Array of Independent/Inexpensive Disks) system, where one or more logical volumes (hereinafter referred to as “logical volumes”) are formed into storage areas provided by one or more hard disk drives.
There are various methods for detecting errors in data recorded on the hard disk drives described above.
First, there is the detection method called “block address check,” involving the steps of: when writing data, adding a block address in a logical volume (Logical Address) to the data; and when reading the data from a hard disk drive, checking the block address added to the data, and the actually read block address. This detection method enables detection of a position error for the data written to the relevant block addresses.
There is another detection method called LRC (Longitudinal Redundancy Check), involving the steps of calculating, for each data block DB, the exclusive disjunction of bit string data sent from a host computer and adding the result of the exclusive disjunction to each data block DB. This detection method enables detection of a bit error in the data blocks DB by adding a parity bit value to each data block DB.
Also, Japanese Patent Laid-Open (Kokai) Publication No. 2007-72571 discloses a method for detecting incomplete data writing by adding a unique value to data upon each write request and verifying the data based on the unique value when reading the data.
Furthermore, Japanese Patent Laid-Open (Kokai) Publication No. S58-125205 discloses a method for detecting a data error in data blocks DB by adding a unique value for data differentiation to data upon each write request and verifying the unique value when reading the data.
However, in the detection methods described above, if the hard disk drive fails to receive an actual write request, the old, non-updated data stored in the hard disk drive is detected and errors in that data are verified instead. Accordingly, any fault in receiving the write request itself cannot be detected.